Questions tagged [rf]
Short for Radio-Frequency. Frequencies at which radiation (intentional or not) plays a role. Typically associated with wireless communications, but also relevant for high-speed PCB design.
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F-parameters instead of S-parameters
What are the F-parameters, how are they computed in CST and what is the relationship between S- and F-parameters?
In CST, they can be obtained, when running the integral solver and having a farfield-...
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2answers
24 views
Colpitts values for NXP's SA605?
I'm trying to put together a simple superhet radio, receiving at 161.75MHz (this is for AIS reception.) I've been trying to design around NXP's SA605 chip (see SA605) but I'm having a hard time ...
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15 views
CST farfield source feeding
Due to a very high structure, I would like to use the Integral Solver in CST. Therefore, I have an antenna and at 10km appart, I am placing a farfield source. The farfield source is taken also from ...
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27 views
Orientation of components for RF Signals
I have been doing the layout for GPS RF part (Frequency: 1.5 - 2 GHz). The components that has to be placed are Bandpass Filters (U25 and U28), LNA (U11) and other ...
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4answers
111 views
How to radiate a positive oscillating voltage?
I am trying to build a simple AM transmitter, transmitting only a carrier wave and thus silencing the noise on my radio standing next to my circuit.
I built this circuit on a breadboard.
It's a ...
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2answers
990 views
what is the purpose of having a “thru cal” on RF PCB?
I often find a thru cal on RF PCB like picture below.
What is the purpose of having this thru cal thing on the board?
One purpose I can think of is to test whether the designed transmission line is ...
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26 views
Questions about stability circle and impedance matching
I'm a RF circuit beginner and got stuck in stability related issues.
According to Pozar's textbook, output stability circle is a contour in the "gamma_L" plane and its arc represents the "gamma_L" ...
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1answer
42 views
Coax cable shielding understanding at AC
I know that AC changes its polarity once a cycle. We use coaxial cable for protecting the signal from magnetic interference. But if the cycle is negative then it it will flow in the shielding, won't ...
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2answers
43 views
Testing the RF properties of an enclosure
I need to measure RF (cellular) blocking properties of an enclosure.
Is there an off-the-shelf set of tools for doing this?
I'm assuming a MHz signal generator and an oscilloscope with an antenna ...
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4answers
92 views
Selecting coaxial cable and connector for PCB referring to required frequency
I want to transmit my 24GHz signal from PCB through coaxial to antenna. I wonder how to chose best match for it, also the power is -5dBm, 50 ohm. It's based on ADF5901 2ch PA. I have found two good ...
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13 views
First order PLL power consumption
For a system level project I want to estimate the impact having a single vs. multiple PLLs.
Is there a first order estimate that relates power, jitter (total integrated phase noise) and possibly ...
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1answer
43 views
How to choose a blocking capacitor for RF power amplifier
I'm using a power amplifier that requires an external blocking capacitor for the input and output ports and I'm trying to decide the best value to use. My understanding of this is that I choose a ...
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1answer
59 views
Does a Vcc layer cause noise to a 4-layer RF PCB?
I'm designing a 4 layer GPS tracker PCB with the 2nd layer as ground and 3rd as Vcc. Is this a good practice? I know a gnd layer is good but I'm not sure how to distribute the positive of the supply ...
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3answers
56 views
How do I terminate a directional coupler?
I'm using a directional coupler for a radar application using frequencies of 5.3-5.9GHz. The directional coupler linked above is matched to a 50ohm characteristic impedance.
How do I terminate the ...
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1answer
61 views
SDR Signal Generator Frontend
I am working on a board that can take the output of an SDR (or VCO) and provide high accuracy amplitude control (+- 0.5dB). This is an opensource project that I will hopefully launch on crowdsupply ...
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1answer
46 views
EN 300 328 CE radio certification with power limit
We have developed product for Malesia country, where we need local SIRIM certificate.
RF module we used in our product is 2.4Ghz wifi mesh, with max 30dbm (1 watt) output power capacity.
To get ...
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1answer
63 views
Contradicting ideas about differential signal route, confining fields vs Increasing impedance
By initial sense I think we must:
keep pair intra-distance as close as possible for field cancellation.
Fill surround of pair with GND plane and have via near to it to confine the fields, prevent ...
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1answer
83 views
Implementation of Decoupling capacitor [closed]
I have schematic for decoupling capacitors (3 set of 0.1uF,1nF,10pF):
And I've implemented that in this way:
And there is ADI reference for easy evaluation:
And the ground pins of decoupling caps ...
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1answer
738 views
90° Bend: Mitered vs Curved
On RF PCBs to bend a trace 90° you have many choices but among them Curved and Mitered bend considered as a good choice from performance POV (Both shown below).
For many years I thought that if you ...
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1answer
46 views
Quadrature modulation Digital to Analog
I want to use an FPGA to generate quadrature modulated signals for use with an RF transceiver (something like MAX2828 ).
I am confused specifically about how the digital to analog modulation should ...
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2answers
26 views
Cellular chip antenna feedline width?
I have a chip cellular antenna from Pulse W3544B. In the datasheet it is said to make the transmission line 1.34 mm thick which I feel is too huge and also I wanted to make a strip line for impedance ...
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0answers
70 views
Can you generate a pure sine wave by mixing a fixed frequency sine wave with a variable frequency square wave?
Let us suppose I don't have a DDS available, and instead I have two square wave clocks with frequencies of my choosing. I have the impression that creating a wide bandwidth (multi-decade) sine wave ...
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0answers
29 views
ESP32: 0.1uF Cap Between SENSOR_VP and SENSOR_VN
According to the ESP32 Hardware Design Guidelines, a 0.1uF cap should be added to the SENSOR_VP and SENSOR_VN pads when using them as an ADC. Why is it then that the subcircuit schematics shown in the ...
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0answers
36 views
Passive (or very low power sensor) sensor to wirelessly receive wake signal
Context. I am using an ESP32 and a small circuit to control an electronic lock on my one of my exterior doors. It is powered by batteries. It has a door magnet sensor to detect when the door is open ...
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1answer
37 views
Struggling with patch gps smd antennas connections
I'm struggling with antenna connections to GPS module in my PCB design.
My antenna is a smd passive patch antenna, "SGGP.25.4.A.02 from Taoglas". The antenna shape and recommended footprint is in the ...
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0answers
53 views
High data rate (~1-5 Mpbs) Point to Point Radio
I'm working on a rocket project at my University, and am trying to find a point to point / point to multipoint radio capable of a hopefully 1-5 Mbps data rate between a ground station a directional ...
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2answers
35 views
does adding Vias through the antenna feed line change impedance?
I have a GPS through-hole patch antenna, the through hole need to be connected to the bottom layer and then from there the feed-line flows to the GPS receiver. But I want the GPS receiver to be on top ...
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0answers
45 views
2.4GHz RF design losing signal
First time poster here, please excuse holes in the plot.
I have a simple wireless design made of an MCU (atmega328p) and an NRF24L01 module, powered through a 3.3V regulator, talking to a similar ...
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1answer
82 views
How to increase range of AM radio waves? [closed]
As a personal project, I made a very simple AM transmitter with an idea from an online tutorial, using a 1 MHz crystal oscillator (plus power source, antenna, breadboard, etc.).
However, when using ...
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1answer
73 views
Are headphones with EMF measurement of 10,000 milligauss harmful to me?
I used a EMF detector app on my phone and measured the EMF output on my wired headphones. It measured around 10,000 milligauss on one part of both ear cups. Since wearing these headphones on my head ...
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0answers
49 views
Discrepancy between simulation and measurement for a voltage doubler/ rectifier design at 5.8 GHz
I am designing a pretty straight-forward voltage doubler at 5.8 GHz with MACOM's MA4E1317 diode, which I have used before and know from previous experience that matches pretty well with the spice ...
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1answer
61 views
Impedance matching for push-pull RF amplifier
I am working on the output matching network of a commercial push-pull class AB amplifier based on LDMOS BLF188. The output matching network consists of a 1:4 transformer and a Toroid with 8 turns The ...
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2answers
43 views
Noise power at receive antenna with finite transmit SNR?
I have seen a few examples of link budgets, and they all assume that the total noise at the Rx is just going to be -174 dBm + 10 log BW. However, this seems to me to assume that the transmit signal is ...
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1answer
82 views
A beginner that could use a few tips on wiring my first circuit involving relays
I am in no way experienced or knowledgeable with circuits or electronics passed installing my own car subwoofers and amps, or swapping out pickups on a guitar which means I only basically know how to ...
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2answers
170 views
Explain this circuit
I know this circuit is an oscillator circuit and it senses another signal of same frequency, but I don't understand
the calculation behind it, and
the reason for emitter inductor,
3.9k collector ...
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0answers
28 views
Impedance matching of a RF power amplifier based on the s2p file
I'm designing the input/output impedance matching circuit for a RF power amplifier, based on the vendor supplied s2p file. I designed separately the input/output matching circuit at the given working ...
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1answer
25 views
XBee Pro Antenna Options - do the U.FL antennas have better range than the chip or micro pad antennas?
Logically the U.FL dipole antenna will have better range than the other two options, as it's a larger antenna, but is this actually true? How do the three antennas perform in relation to each other ...
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2answers
60 views
Question about the power rating of a RF power amplifier
In HMC453ST89's datasheet, it gives the electrical specifications when Vs = +5V:
The max. output power is around 32.5dBm, about 1.6W. But for a 50 Ohm load, 1.6W means the peak voltage is about 12V. ...
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1answer
56 views
How close to P1dB can I go?
I'm trying to decide on a safe input power to a power amplifier. The amplifier in question is SE5004L. The datasheet specifies that the amplifier output 1-dB compression point has a minimum value of ...
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2answers
121 views
Can somebody please explain the antenna and mixer stage of this AM superheterodyne receiver?
This is from an Elenco AM/FM superheterodyne radio receiver kit.
The shown area is the AM antenna and mixer stage. The wire leading from the top right corner is Vcc.
Q7 simultaneously oscillates ...
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2answers
79 views
Project - How to onstruct a circuit to introduce and control a 0-300ms delay in an RF feed from a Sky Box to multiple TV sets? [closed]
Just bought a new TV!
It's "smart" but where my previous dumb TV didn't, my smart TV introduces a delay over HDMI from my Sky+HD box compared to the RF2 output which is wired via coax cable to the ...
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5answers
1k views
How do microstrips actually represent lumped components?
I'm having trouble understand intutively how microstrips repersent lumped element components.
All we are told is that, high impedance sections on a microstrip line repersent inductors and low-...
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1answer
29 views
How to stop erroneous signals on startup of an RF circuit
I have a really janky setup where I'm using an ESP and some transistors to "push" the buttons on an RF remote control, used for controlling electrical outlets. The circuit works perfectly during ...
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0answers
32 views
Creating a balanced dipole from two monopole chip antennas for use on small PCBs
I'm trying to use a monopole chip antenna on a PCB much smaller than the one recommended in the datasheet. I am wondering if I can get away with a much smaller board by using two monopole antennas ...
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2answers
70 views
I don't know how to choose an adequate antenna
I need to choose an antenna for a long range free space communication (~10km), and I currently have a receiving antenna, but I don't understand enough to be able to pick an adequate emitter.
The ...
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1answer
33 views
Equivalent Series Resistance of 13.56 MHz RFID Antenna
I am designing a system that uses the MFRC522 by NXP Semiconductors and I am having a bit of difficulty designing the antenna.
NXP provide an antenna design guide under the application note AN1445 ...
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1answer
68 views
How to design RF PCB to ensure the 50 ohm impedance
I do not have any experience designing RF circuits and I am finding many challenges for my project.
One of them is to match the 50 ohm impedance that some components demand. In the input of my PCB I ...
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1answer
51 views
My mobile detector circuit won't work
I'm trying to get C3 to detect RF signals from a mobile phone. Amplify this signal to detect it using an LED.
My main issue is simulating the antenna on multisim since multisim doesnt have an antenna!...
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1answer
74 views
Generating a realistic sine wave in MATLAB
I'm working on a simulation on MATLAB and I need a realistic sine wave which has harmonics. So I know there would be harmonics at 2f,3f... but I am not sure how to determine their amplitude. I tried ...
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1answer
54 views
How to find new ABCD parameters when reversing 2-port network
I have an ABCD matrix represenataion which is defined as:
For such a problem, what approach should I follow in order to organize the new ( reversed) network ports voltages and currents properly. I ...
